1. Field of the Invention
The present invention relates to isolated polypeptides having glucoamylase activity and isolated nucleic acid sequences encoding the polypeptides. The invention also relates to nucleic acid constructs, vectors, and host cells comprising the nucleic acid sequences as well as methods for producing and using the polypeptides.
2. Description of the Related Art
High dextrose and fructose syrups are made by enzymatic saccharification of liquefied starch. The saccharification is achieved by means of a dextrose-forming exo-amylase known as exo-1,4-alpha-D-glucosidase (glucoamylase or amylogulcosidase). The enzyme hydrolyzes 1,4-as well as 1,6-alpha-linkages in starch. During hydrolysis, glucose units are removed in a step-wise manner from the non-reducing ends of the substrate molecule, whereas the 1,6-alpha-linkages found in branched dextrins are broken down relatively slowly. Maltotriose and maltose are hydrolyzed at a lower rate than higher oligosaccharides. Glucoamylases are also used to lower the carbohydrate content of beer.
Thielavia terrestris is a thermophilic filamentous fungus that can grow at low pH of 4.5 and elevated temperature of 40-45.degree. C. (WO 96/02653). The ascomycete has a wide geographic distribution and a homothallic mating behavior (Mouchacca, 1997, Cryptogamie Mycol. 18: 19-69). Several enzymes are known to be produced by Thielavia including xylanase, glucanase, cellulase, glucosidase, mannanase, and galactanase.
There is a need in the art for new sources of glucoamylase with improved properties of thermostability.
It is an object of the present invention to provide improved polypeptides having glucoamylase activity and nucleic acid encoding the polypeptides.